Q. Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of
A) CrSO₄
B) Cr₂(SO₄)₃
C) CrO₄²⁻
D) Cr₂(SO₃)₃
Explanation
[Solution from source] Sulphite reduces dichromate in acid: Cr₂O₇²⁻ + 3SO₃²⁻ + 8H⁺ → 2Cr³⁺ + 3SO₄²⁻ + 4H₂O. The green colour is due to Cr³⁺, i.e. Cr₂(SO₄)₃. Chromate is yellow and Cr would not be reduced to +2. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.